Acrolein is a simple unsaturated aldehyde compound which includes incomplete reactive groups to have high reactivity, and is used as a major intermediate for synthesis of numerous chemicals. In particular, acrolein has been widely used as an intermediate for synthesis of acrylic acids, acrylic acid esters, superabsorbent polymers, animal feed supplements, or food supplements.
Such acrolein has been mainly prepared by selective gas-phase oxidation of a starting material, propylene, which is obtained during petroleum cracking, with atmospheric oxygen. However, as fossil fuels have been reduced and environmental problems such as the greenhouse effect have emerged, many studies have been conducted to develop a method of preparing acrolein using non-fossil fuel-based renewable materials.
Therefore, glycerin, which is a natural by-product obtained from biodiesel production, has received much attention as a raw material for acrolein preparation. In particular, the growth of biodiesel production increases the size of the glycerin market, and industrial application of glycerin has been studied due to its low price.
For example, a method of obtaining a mixture of acrolein and acrylic acids by glycerin dehydration in the presence of a catalyst is known. The dehydration reaction of glycerin proceeds in a gas phase oxidation reaction in the presence of a catalyst, and the use of a catalyst is essential.
However, there is a problem that the catalyst is deactivated, because by-products such as hydroxypropanone, propane aldehyde, acetaldehyde, polycondensation products of glycerin, cyclic glycerin ether, phenol, or polyaromatic compound are formed as the dehydration reaction of glycerin proceeds, and then coke carbon is deposited on the catalyst. Therefore, efforts have been made to develop a catalyst having an increased lifetime that may be continuously operated by inhibiting deposition of the coke carbon.
Accordingly, there is a need to develop a catalytic reaction system capable of removing coke carbon so as to minimize the production of by-products which generate coke carbon or to maintain the activity of the catalyst during the reaction.